This paper provides an overview of research on core from Oman Drilling Project Hole BT1B and the surrounding area, plus new data and calculations, constraining processes in the Tethyan subduction zone beneath the Samail ophiolite. The area is underlain by gently dipping, broadly folded layers of allochthonous Hawasina pelagic sediments, the metamorphic sole of the Samail ophiolite, and Banded Unit peridotites at the base of the Samail mantle section. Despite reactivation of some faults during uplift of the Jebel Akdar and Saih Hatat domes, the area preserves the tectonic “stratigraphy” of the Cretaceous subduction zone. Gently dipping listvenite bands, parallel to peridotite banding and to contacts between the peridotite and the metamorphic sole, replace peridotite at and near the basal thrust. Listvenites formed at less than 200°C and (poorly constrained) depths of 25 to 40 km by reaction with CO2-rich, aqueous fluids migrating from greater depths, derived from devolatilization of subducting sediments analogous to clastic sediments in the Hawasina Formation, at 400-500°. Such processes could form important reservoirs for subducted CO2. Listvenite formation was accompanied by ductile deformation of serpentinites and listvenites – perhaps facilitated by fluid-rock reaction – in a process that could lead to aseismic subduction in some regions. Addition of H2O and CO2 to the mantle wedge, forming serpentinites and listvenites, caused large increases in the solid mass and volume of the rocks. This may have been accommodated by fractures formed as a result of volume changes, perhaps mainly at a serpentinization front.

Integrating detrital zircon U/Pb and whole-rock Nd data throughout the Himalayan arc provides the means to distinguish between the Tethyan (TH), Greater (GH), and Lesser Himalayan (LH) tectonostratigraphic zones within the thrust belt. In the Kaghan valley of northern Pakistan, debate exists over the existence and location of the Main Central thrust (MCT) and the tectonostratigraphic affinity of the rocks in the Hazara-Kashmir syntaxis. Three new detrital zircon U/Pb age spectra and two new εNd(0) values from the footwall rocks of the Batal fault yield 1.0-2.0 Ga age populations and an average εNd(0) value of -13.6. Four new detrital zircon U/Pb age spectra and two new εNd(0) values from the hanging wall rocks have primarily <1.2 Ga age populations and an average εNd(0) value of -16.7. Most detrital zircon analyses exhibit Pb-loss from younger (<600 Ma) intrusive or metamorphic events. The absence of zircon <1.0 Ga in the footwall samples indicates that they are LH rocks, while εNd(0) values indicate that they are not Paleoproterozoic LH rocks, but are comparable to other Meso- and Neoproterozoic LH rocks along the Himalayan arc. Neoproterozoic and younger detrital zircon age populations from the hanging wall samples and the presence of ~47 Ma intrusive leucogranite indicate that these are either TH or GH rocks, with εNd(0) values also consistent with TH or GH values. Combining these data show that the hanging wall rocks are either TH or GH rocks, and that the footwall rocks are Mesoproterozoic LH rocks. In most places, the MCT is defined as GH rocks thrust over LH rocks. However, in NW India, the GH/LH contact is buried in the subsurface, and the MCT at the surface is a TH/LH contact. Therefore, these data define the Batal fault in the Kaghan valley as equivalent to the MCT, with TH/GH rocks thrust over LH rocks, and link it with the Indus River valley to the west in Pakistan and NW India to the east.

Lava domes form by the effusive eruption of viscous lava and are inherently unstable and prone to collapse. Dome collapses can generate pyroclastic flows and trigger explosive eruptions and thus represent a significant natural hazard. Many processes may contribute to the instability and collapse of lava domes, including advance of the dome margins, overtopping of confining topography, internal gas overpressure, and gravitational instability of the dome structure. Collapses that result from these processes can generally be grouped into two types: active and passive. Active collapses are driven by processes associated with active lava effusion, (e.g. dome growth or gas pressurization), while passive collapses are not directly associated with eruptive activity and can be triggered by overtopping of topographic obstacles or weakening of the dome structure. We use data collected by uncrewed aerial systems (UAS, commonly called ‘drones’) and a slope stability model to both identify and assess the stability of potential collapse sites for both passive and active processes. We collected visual and thermal infrared images by UAS and used structure-from-motion photogrammetry to generate thermal maps and digital elevation models (DEMs) of two example lava domes at Sinabung Volcano (Sumatra, Indonesia) and Merapi Volcano (Java, Indonesia). We evaluate the stability of erupted lava using the Scoops3D numerical model to assess the risk of passive and active collapses, including an assessment of the effect of lava material properties and internal pore pressure on the dome stability. We compare the collapse risk from Scoops3D with UAS-derived temperature maps and DEM differencing to evaluate the stability, size, and location of observed or potential collapses. We test whether Scoops3D can hindcast the sites and magnitudes of passive collapses at Sinabung that occurred in 2014 and 2015 and assess the stability of the remaining lava dome (growth has ended in spring 2018). For both volcanoes. Through application of these techniques, we are able to evaluate the collapse risk due to multiple processes that may act contemporaneously to generate dome instability. This study demonstrates how identification and classification of individual collapse mechanisms can be used to assess hazards at dome-forming volcanoes.

We describe a three-dimensional discrete fracture hybrid model (DFHM) that returns forecasts of both induced seismicity and of power generation in an Enhanced Geothermal System (EGS). Our model considers pore-pressure increase as the mechanism driving induced seismicity, similarly to other hybrid models, but it employs discrete fracture modelling for flow and heat that allows accurate and realistic transient solutions of pore pressure and temperature in fractured reservoirs. Earthquakes and flow are thus considered as closely coupled processes. In the DFHM model, the creation phase of an EGS is described as a Markovian process with a transitional probability that encapsulates the irreducible uncertainty with regards to induced seismicity. We conditioned this transitional probability on field observations from the 2006 EGS project in Basel, achieving a good match with observations of seismicity evolution. Specifically, our model effectively reproduces and explains the observed long-term exponential decay of seismicity after the well was shut in, suggesting that pore pressure diffusion in a critically stressed fractured reservoir is sufficient to explain long-lasting post-injection seismic activity as observed in Basel. We then investigate alternative injection scenarios, using Monte Carlo simulations to capture the uncertainties in fault locations and stressing conditions. We show that the number of induced events depends not only on the total injected volume but also on the injection strategy. We demonstrate that multi-stage injection schemes are superior to single-stage ones, since the former are associated with less seismic risk and can generate at least the same revenue in the long term.

To better understand the mechanisms of crustal exhumation related to tectonic extension, we report on the progressive doming and detachment faulting of the Cretaceous Liaonan metamorphic core complex (MCC). The detachment fault zone of Liaonan MCC is comprised of two branches, i.e., the Jinzhou detachment fault zone (JDFZ) and the poorly-researched Dongjiagou shear zone (DSZ). Thus, integrated structural, microstructural, quartz c-axis fabrics, and fluid inclusion analysis, and U-Pb on zircon dating were performed on mylonites along the DSZ. In contrast with the JDFZ that possesses characteristics of detachment fault zone, the DSZ encompasses Archean gneisses and Neoproterozoic meta-sedimentary rocks, between which exists an obvious metamorphic contrast forming a tectonic discontinuity contact (TDC). However, rocks from both sides of the TDC possess structures and fabrics for identical geometries and kinematics that are consistent with those along the JDFZ. Thermometric analysis of fluid inclusions from syn-tectonic quartz veins (630 °C, 470 °C, 350 °C) and quartz c-axis fabric from mylonites along the DSZ show that the shearing penetrates throughout the Archean to Neoproterozoic rocks. Dating of zircons from syn-kinematic granitic dikes from DSZ yields an age ca. 134 Ma, which is similar to the ages of early shearing along the JDFZ (ca. 133~134 Ma). The results imply that the shearing initiated in both JDFZ and DSZ at an early stage, then progressive shearing continued, and finally developed the detachment faulting along the JDFZ. Based on the timing and processes of the regional extension, a geodynamic model of MCC’s is proposed.

Awu is one of the remote and little known active volcanoes of Indonesia. It is the northernmost active volcano of Sangihe arc with 18 eruptions in less than 4 centuries, causing a cumulative death toll of 11048. Two of these eruptions were classified as VEI 4. Since 2004, a lava dome occupies the center of Awu crater, channeling the fumarolic gas output along the crater wall. A combined DOAS and MultiGAS measurements highlight a relatively small SO degassing (13 t/d) into the atmosphere. In contrast the measurements spotlight an elevated and non-negligible CO emission into the atmosphere of 2600 t/d, representing 1% of the global CO emission budget from volcanoes. The cause for this high CO degassing may reside in the peculiar geodynamic context of the region, where the slowing down of arc-to-arc collision has enhanced heating of the slab, leading to greater production of fluid rich in carbon.

The utilization of first-order information about seafloor morphology, derived from multibeam sonar data, has become common in the investigation of deep-sea benthic habitats. When combined with complementary datasets, these data can be used to study deep-sea coral ecosystems and predict environments that are favorable for fish spawning, larval nurseries, and juvenile fish habitats. The identification and protection of these environments is critical where biodiversity is vulnerable or unique in order to rehabilitate or maintain ecological communities and encourage higher fecundity. In August of 2019, the expedition Deep Connections: Exploring Atlantic Canyons and Seamounts was conducted to explore understudied deep-sea environments aboard the NOAA Ship Okeanos Explorer off the coast of the United States and Canada (EX1905L1 and EX1905L2). This expedition included multibeam mapping and seafloor exploration with a Remotely Operated Vehicle (ROV). Observations from ROV dives include several fish species including multiple sightings of Atlantic halibut (Hippoglossus hippoglossus), which is considered endangered on the International Union for Conservation of Nature Red List of Threatened Species. Identifying and classifying the habitats where Atlantic halibut is observed would facilitate future endeavors of protection or rehabilitation. Spawning events are known to coincide with areas of increased seafloor slope associated with high energy systems such as canyons. Utilizing multibeam data included in the Global Multi-Resolution Topography (GMRT) Synthesis, we characterize canyons at the edges of George’s and Brown’s Banks based on morphology, roughness, and seafloor slope and aspect. We combine these data with observations of Atlantic halibut from ROV video to seek correlations that can be used to identify potential habitats. This information can be used to guide further exploration and characterization of the seafloor to better understand the spatial extent of Atlantic halibut habitat in the region.

The story the Antarctic Core Collection’s (ACC) transition from Florida State University (FSU) to Oregon State University (OSU) is one of the largest-scale data rescue efforts in recent history. The ACC is the world’s largest collection of seafloor sediment samples from the Southern Ocean. The collection was officially established in 1963 as the US Antarctic Program took shape. For the next fifty years, the collection grew to represent the scientific discoveries of over one-hundred and twenty research cruises and expeditions around Antarctica. FSU hosted the irreplaceable collection at its Antarctic Research Facility, an iconic lab in the center of campus. In 2016, the university chose not to renew its contract for supporting the facility. Recognizing the value and potential of the collection, the National Science Foundation began a search for another university to host these important samples and enable future research. In 2017, OSU’s Marine and Geology Repository (OSU-MGR) initiated a plan to relocate this historic collection of over eighteen kilometers of core samples from Tallahassee, FL to Corvallis, OR. The project began by planning and constructing a state-of-the-art facility with temperature-controlled space to house the next fifty years of coring expeditions to the Southern Oceans and beyond. In the summer of 2018, the ACC was carefully packaged, digitally inventoried, and shipped to OSU. In this process, the OSU-MGR staff have worked to improve metadata records to build an effective modern inventory of the ACC using new digital collection management techniques, including QR coded labels and scanners. These metadata are managed on tablets with the OSU-MGR App and indexed in an Elasticsearch cluster to streamline the repository’s workflows and to display summary statistics. Current and future curation projects will comply with FAIR data principles, with the goal of making all OSU-MGR collections and associated datasets more easily discoverable online.

The University of Houston’s USIP (Undergraduate Student Instrument Project) Remote Sensing team is designing and building an airborne LiDAR with the intention of using it to 3D map landslides and for possible mineral exploration. The maps will be used to conduct landslide analyses and failure predictions while the magnetometer feedback will be used to determine the presence of possible metallic minerals in the area. The LiDAR will employ the use of two lasers with different output wavelengths; 1550nm will be used for typical terrain mapping and 532nm will be used for snow depth reading to extrapolate the underlying terrain characteristics. Trade studies are currently underway for the lasers, sensors, IMU’s and magnetometers. It is planned for the LiDAR to collect data near Fairbanks, Alaska, with further research into potential study sites being conducted. The scan pattern is still being decided on with the most likely option being a circular scan for the 532nm laser and a zig zag pattern for the 1550nm laser both set at a maximum scan angle of 20 degrees. The Remote Sensing team has been facing unforeseen obstacles due to the nature of the COVID-19 pandemic. Upon initial lockdown, weekly scheduled in person meetings and lab work were prohibited. After the first week, though, new mediums of communication were established. The USIP group decided to conduct online meetings through Microsoft Teams and use Slack for text-based communication outside of meetings. Unfortunately, lockdown and COVID chaos brought psychological issues to group members that can be difficult to overcome. This included high stress levels caused by the chaotic events as well as isolation-induced depression. After some deliberation amongst all USIP groups, it was decided to occasionally hold non work-related meetings through Microsoft Teams. This reduced some of the isolation depression by relaxing, talking, and eating pizza. After lockdown restrictions were lifted, the university had begun preventing the previous number of students from being in the lab at once. On top of that, individuals were understandably hesitant to go to the lab, often opting out. Despite this, small groups of USIP students have been going to the labs to clean, disinfect, and get the lab ready for work. New lab procedures have also been created to adhere to social distancing norms.

Gravity currents frequently occur when excess suspended sediments are flushed along a river and discharged into greater natural water environments such as lakes, reservoirs, and estuaries. Gravity and turbidity currents have been broadly investigated, but the effect of aquatic vegetation on their propagation in natural waters still presents several open questions. We conducted a series of laboratory experiments to investigate how flexible vegetation affects the propagation and flow structure of gravity currents on a constant slope. We used both rigid cylinders and flexible synthetic plants to mimic natural submerged vegetation canopies. By varying density configurations of the vegetation array and comparing the outcomes of rigid cylinders and flexible plants, the data showed distinct patterns based on array density and plant morphology. A two-layer current was created when the array density is large enough to redirect the flow, as opposed to sparser conditions where the denser fluid passes swiftly through the array. Flexible vegetation further suppresses the propagation speed of gravity currents compared to arrays of rigid cylinder with the same density, highlighting the importance of the multi-scale processes driven by complex plant morphologies that are not represented by rigid cylinder arrays.

Turbulence generated by aquatic vegetation in rivers, lakes, and estuaries, can significantly alter the flow structure throughout the whole water column, affecting gas transfer mechanisms at the air-water interface, driving changes in indicators of water quality. We conducted a series of laboratory experiments with rigid cylinder arrays to mimic vegetation using a staggered configuration in a recirculating Odell-Kovasznay type race-track flume. 2D planar Particle Image Velocimetry (PIV) was used to characterize the mean flow field and turbulent flow statistics, to characterize the effect of emergent and submerged vegetation in terms of turbulent kinetic energy, Reynolds stresses, and turbulent shear production. The surface gas transfer rate was determined by measuring the dissolved oxygen (DO) concentration during the re-aeration process in water based on the methodology proposed by the American Society of Civil Engineers (ASCE). Our data provide new insight on how stem- and canopy- scale turbulence affect the surface gas transfer rate at different submergence ratios and array densities. The relation between mean flow velocity and turbulent shear production in these scenarios is used to develop a modified surface renewal (SR) model using turbulent shear production as an indicator of gas transfer efficiency, which allows us to more accurately predict surface gas transfer rates in vegetated flows.

Why is plane-bed topography unstable under certain flow conditions? We investigate the grain-scale mechanisms responsible for topographic instability at the onset of bedform development. Measurements of fluorescent tracer particle motion were used to estimate the ensemble mean particle activity, entrainment rate, hop distance, travel time, and particle velocity characteristic of flow conditions straddling the threshold stress for bedform development. Based on these data, we propose two hypotheses to explain the destabilization of planar topography with rising transport conditions. Hypothesis 1: plane-bed topography is unstable above a theory-predicted entrainment rate threshold that varies primarily as a function of particle diameter. Hypothesis 2: plane-bed topography is unstable above a threshold particle collision frequency that is proportional to bedload flux.The threshold particle collision frequency is predicted analogously to the propensity for congestion shockwaves in vehicular traffic flow theory.

This paper focuses on the study of the temporal evolution of seismicity and the role of fluids during major earthquake sequences that occurred in the central Apennines and Eastern California Shear Zone-Walker Lane belt over the last two decades: The 1997 Colfiorito sequence, the 2009 L’Aquila sequence, the 2016 Amatrice-Norcia sequence, and the 2019 Ridgecrest sequence. The availability of different high-quality seismic catalogs offers the opportunity to evaluate in detail the temporal evolution of the earthquake’s size distribution (or b-value) and propose a physical explanation based on the effect of the fluid flow process in triggering seismicity. For all seismic sequences, the b value time series show a gradual decrease from a few months to one year before mainshocks. The gradual decrease in the b value is interpreted in terms of coupled fluid-stress intensity as a gradual increase in earthquake activity due essentially to the short-term to intermediate-term pore-fluid fluctuations. For the 2016 Amatrice-Norcia sequence and the 2019 Ridgecrest sequence, the temporal variation of b value during the foreshock sequence is characterized by a double b value minimum separated by a short-lived b value increase as observed in laboratory experiments on water-saturated rocks. Based on laboratory experiments results, the observed short–term fluctuation of b value is presented here as an accelerating cracks growth due essentially to the fluid flow instability. Despite that the occurrence of seismic precursors could have been predictable in areas with high dense seismic networks, the different b value time series show difficulty to establish a correspondence between the duration of the foreshock activity and the magnitude of the next largest expected earthquake. This may suggest that the spatial and temporal evolution of fluid migration controls the size of the ruptures.

Seamounts are isolated elevations in the seafloor with circular or elliptical plan, comparatively steep slopes, and relatively small summit area (Menard, 1964). The vertical gravity gradient (VGG), which is the curvature of the ocean surface topography derived from satellite altimeter measurements, has been used to map the global distribution of seamounts (Kim & Wessel, 2011). We used the latest grid of VGG to update and refine the global seamount catalog; we identified 10,796 new seamounts, expanding the catalog by 1/3. 739 well-surveyed seamounts, having heights ranging from 421 m to 2500 m, were then used to estimate the typical radially-symmetric seamount morphology. First, an Empirical Orthogonal Function (EOF) analysis was used to demonstrate that these small seamounts have a basal radius that is linearly related to their height – their shapes are scale invariant. Two methods were then used to compute this characteristic base to height ratio: an average Gaussian fit to the stack of all profiles and an individual Gaussian fit for each seamount in the sample. The first method combined the radial normalized height data from all 739 seamounts to form median and median-absolute deviation. These data were fit by a 3-parameter Gaussian model that explained 99.82% of the variance. The second method used the Gaussian function to individually model each seamount in the sample and further establish the Gaussian model. Using this characteristic Gaussian shape we show that VGG can be used to estimate the height of small seamounts to an accuracy of ~270 m.

For more than 150 years, geological features claimed to be evidence for pre-Pleistocene glaciations have been debated. Advancements in recent decades, in understanding features generated by glacial and mass flow processes, are here reviewed. It is timely to make renewed comparisons and to re-visit the interpretations of data used to support pre-Pleistocene glaciations. Similarities and differences of Quaternary glaciogenic and sediment gravity flow features, which are most often referred to as proxies and evidence of ancient glaciations, are documented, discussed and closely examined, in order to uncover the origin of more ancient deposits. It is necessary to use multiple proxies to develop a correct interpretation of ancient strata. Analyses and evaluation of data are from a) Quaternary glaciations and glaciers, b) formations which have been assigned to pre-Pleistocene glaciations, and c) formations with comparable features associated with mass-flow deposition (and occasionally tectonics). The aim is not to reinterpret specific formations and past climate changes, but to enable data to be evaluated using a broader and more inclusive conceptual framework. To achieve this goal, detailed descriptions of field evidences are documented from papers that may suggest different interpretations of these data. This is not in an intention to present revised interpretations of these papers, but to collect data and develop a foundation for enhanced analysis of geologic processes and features. Regularly occurring features interpreted to be glaciogenic and are contemporaneous with pre-Pleistocene diamictites which have been interpreted to be tillites, have often been shown to have few or no Quaternary glaciogenic equivalents. These same features commonly form by sediment gravity flows or other non-glacial processes, which may have led to misinterpretations of ancient deposits. These features include, for example, appearances and documented data from the extent and thickness of diamictite deposits, environmental and depositional affinity of fossils in close connection to diamictites, grading and bedding of diamictites, fabrics, size of erratics, polished and striated clasts and surfaces (“pavements”), boulder pavements, lineations, valleys, glaciofluvial deposits, dropstones, laminated sediments, glaciomarine sediments, periglacial structures, soft sediment tectonics, and surface microtextures. The analysis of these features provide detailed documentation that may be used to help identify the origin for many pre-Pleistocene diamictites. Recent decades of progress in research relating to glacial and sediment gravity flow processes has resulted in proposals by geologists, based on more detailed field data, more often of an origin by mass movements and tectonism than glaciation. The most coherent data of this review, i.e. appearances of features produced by glaciation, sediment gravity flows and a few other geological processes, are summarized in a Diamict Origin

Subtle elastic rock deformation during aquifer testing may bear hydraulic parameter (permeability and compressibility) information owing to the poroelastic hydromechanical coupling effect. Here we report that such in situ rock deformations (~50 µε) during an aquifer pumping test are successfully measured along a vertical well by a high-resolution fiber optic distributed strain sensing (DSS) tool with an accuracy of 0.5 µε. We investigate the feasibility of hydraulic parameter estimation at meter scale using DSS data through a coupled hydromechanical model. Both synthetic and field cases are tested with sensitivity analysis. The results indicate that the simultaneous estimation of permeability and compressibility using DSS data is possible at low noise levels. However, only non-global near-optimal solutions can be obtained using the applied gradient-based inversion algorithm, because of parameter crosstalk and sensitivity problems when the data contain large noise. In particular, estimation is difficult for zones with relatively low permeability due to the low sensitivity to the strain changes. The estimated permeability/compressibility structures for the field test are largely consistent with other geological information from well logs. Our study suggests that DSS data can be quite useful in aquifer characterization and fluid flow profiling in addition to geomechanical monitoring. The obtained hydraulic information is beneficial for the optimized reservoir management of water and oil/gas storage.

High-resolution space-based spectral imaging of the Earth’s surface delivers critical information for monitoring changes in the Earth system as well as resource management and utilization. Orbiting spectrometers are built according to multiple design parameters, including ground sampling distance (GSD), spectral resolution, temporal resolution, and signal-to-noise. The different applications drive divergent instrument designs, so optimization for wide-reaching missions is complex. The Surface Biology and Geology component of NASA’s Earth System Observatory addresses science questions and meets applications needs across diverse fields, including terrestrial and aquatic ecosystems, natural disasters, and the cryosphere. The algorithms required to generate the geophysical variables from the observed spectral imagery each have their own inherent dependencies and sensitivities, and weighting these objectively is challenging. Here, we introduce intrinsic dimensionality (ID), a measure of information content, as an applications-agnostic, data-driven metric to quantify performance sensitivity to various design parameters. ID is computed through the analysis of the eigenvalues of the image covariance matrix, and can be thought of as the number of significant principal components. This metric is extremely powerful for quantifying the information content in high-dimensional data, such as spectrally resolved radiances and their changes over space and time. We find that the intrinsic dimensionality decreases for coarser GSD, decreased spectral resolution and range, less frequent acquisitions, and lower signal-to-noise levels. This decrease in information content has implications for all derived products. Intrinsic dimensionality is simple to compute, providing a single quantitative standard to evaluate combinations of design parameters, irrespective of higher-level algorithms, products, applications, or disciplines.

The India-Asia continental collision, starting at ~50 Ma, has resulted in about 2000 km crustal shortening to build the Himalaya-Tibetan plateau, which is one of the landmark terrestrial features on the Earth. In this study, using a thin viscous sheet approximation we performed scaled laboratory model experiments to investigate the spatiotemporal variation in the Himalaya-Tibetan tectonics. The experiments allow us to constrain the Tibetan plateau topography as a function of the varying India-Asia convergence rates. Our results suggest two rigid crustal blocks: Tarim and Sichuan basins steered the growth pattern in the Tibetan plateau. Because of the resistance from the rigid Tarim block western Tibet uplifted first relative to eastern part, creating a topographic elevation difference, which directed the crustal flows grossly to NE. We show from experiments the elevated plateau topography underwent gravitational collapse when the indentation velocity dropped to present average of ~3.5 cm/yr at around 18 Ma. This event eventually led to a transition from contraction to extensional tectonics, dominated by east-directed crustal flows in response to the eastward topographic gradient developed during the early stage of fast collision. We compare the present day crustal flow velocity field, strain rates, and topographic variations in the model Tibet with the actual observations in the Himalaya-Tibet Mountain System.

Global tomographic models have revealed the existence of two large low shear-wave velocity provinces (LLSVPs) underlying Africa and the Pacific, which are regarded as sources of most typical mantle plumes. Plume-induced basalts have the potential to imply the formation mechanisms and evolutional histories of the LLSVPs. In this study, we measured H2O contents in clinopyroxene and olivine phenocrysts from Cenozoic basalts produced by the Kerguelen and Crozet mantle plumes, which are deeply rooted in the African LLSVP. The results were used to constrain the H2O content in the source of basalts, yielding 1805 ± 579 ppm for the Kerguelen plume and 2144 ± 690 ppm for the Crozet plume. H2O contents in the mantle sources of basalts fed by other plumes rooted in these two LLSVPs were calculated from literature data. Combining these results together, we show that the African LLSVP seems to have higher H2O content and H2O/Ce (620-2144 ppm and 184-592, respectively) than the Pacific LLSVP (262-671 ppm and 89-306, respectively). These features could be ascribed to incorporation of subducted material, which had experienced variable degrees of dehydration during its downwelling, into the LLSVPs. Our results imply that the continuous incorporation of subducted oceanic crust modifies the compositions of LLSVPs and induces heterogeneous distribution of H2O within individual LLSVPs and distinct H2O contents between the African and Pacific LLSVPs. This suggests that the African and Pacific LLSVPs might have different formation and evolution histories.

Recent developments in space-based surveying methods of Earth’s topography, including the differential synthetic aperture radar interferometry (DInSAR), increased the availability of options for monitoring of land subsidence. However, DInSAR methods require expert knowledge, specialized software, and are time-consuming. Here, we demonstrate that a land subsidence signal in the difference of freely available global digital elevation models (DEMs), e.g., SRTM and TanDEM-X, is identifiable using a simple statistical method. This finding opens up a venue to develop a dedicated computer application to identify land subsidence or uplift of the order > 20 mm yr. Such an application would allow for the monitoring of the impacts of underground mining, earthquakes, landslides, volcanic activities, and similar effects on the Earth’s topography. This software will provide a useful and cost-effective approach to scan the global DEMs for the benefit of many land planning and management agencies around the world.

Unsaturated fractured aquifer systems offer a domain for complex gravity-driven flow dynamics leading to the development of preferential flow along fracture networks that often strongly contributes to rapid mass fluxes. This behaviour is difficult to recover by volume-effective modeling approaches (e.g. Richards equation) due to the non-linear nature of free-surface flows and mass partitioning processes at unsaturated fracture intersections. The application of well-controlled laboratory experiments enables to isolate single aspects of the mass redistribution process that ultimately affects travel time distributions across scales. We use custom-made acrylic cubes (20 cm x 20 cm x 20 cm) in analogue percolation experiments to create simple fracture networks with single or multiple horizontal fractures. A high precision multichannel dispenser produces gravity-driven free surface flow (droplets; rivulets) at flow rates ranging from 1 ml/min to 5 ml/min. Hereby, total inflow rates are kept constant while the fluid is injected via 15 (droplet flow) or 3 inlets (rivulet flow) to reduce the impact of erratic flow dynamics. Normalized fracture inflow rates (Q_f/Q_0) are calculated and compared for aperture widths d_f of 1 mm and 2.5 mm. A higher efficiency in filling an unsaturated fracture by rivulet flow observed in former studies can be confirmed. The onset of a capillary driven Washburn-type flow is determined and recovered by an analytical solution. In order to upscale the dynamics and enable the prediction of mass partitioning for arbitrary-sized fracture cascades a Gaussian transfer function is derived that reproduces the repetitive filling of fractures, where rivulet flow is the prevailing regime. Results show good agreement with experimental data for all tested aperture widths.

Experimental study of the phase and amplitude observations of sub-ionospheric very low and low frequency signals is performed to analyze the response of the lower ionosphere during the August 21, 2017 total solar eclipse in the United States of America. Three subionospheric wave paths have been investigated. The length of the paths varied from 2200 to 6500 km, signal frequencies were 21.4 kHz, 25.2 kHz and 40.8 kHz. Two paths crossed the region of total eclipse and the third path was in the region of 40-60% of obscuration. None of the signals revealed any noticeable amplitude changes during the eclipse while negative phase anomalies (from -35° to -95°) were detected for all three paths. It was shown that the effective reflection height of the ionosphere in low and middle latitudes has been increased by 3.5-5 km during the eclipse.

High concentration of fluoride in the groundwater is observed to be associated with granitic aquifers as well as near phosphate mines around the globe. The present work is a hydrogeological study of the ground water of Beldih phosphate mines in India. Being located in the Singhbhum shear zone the area has a complex tectonic history and is dominated by phosphate, alkali granites, amphibolites, and granitic gneiss with higer abundance of fluoride bearing minerals like apatite and biotite. Total of 12 water samples were collected for a preliminary study to assess the spatial variation of fluoride in ground water and surface water with an aim to understand the effect of phosphate mines in elevating fluorosis in adjoining areas. The groundwater chemistry shows a trend that the concentration of fluoride and nitrate gets elevated as we approach towards the open cast phosphate mines. From the spatial observation combined with the water chemistry and geology it is evident that the apatite dissolution is the prime cause of the elevation in fluoride concentration. However presence of iron in the lithology controls the fluoride level to some extent. Since the area is effected with high fluorosis its can be concluded that the groundwater geochemistry along with the air borne fluoride present in the phosphate dust are the major cause of the fluorosis. The exploration of phosphate must be carried out with out most environmental care and the mitigation of post mining effect should be planned before mining operation. Fluorosis is an irreparable health hazard and a major geohealth concern that has already affected a large amount of population.

Transmission muography is an expanding technique based on the attenuation of the natural-occurring cosmic muons flux due to the opacity of the medium to obtain the distribution of density around the detector. The current work introduces the technology developed by the Temporal Tomography of the Densitometry by the Measurement of Muons (T2DM2) collaboration. The MUST2 camera leans on a thin time projection chamber read by a resistive Micromegas. This new tool presents interesting distinctive features, allowing a wide angular acceptance of the detector with a low weight and volume, well adapted for confined spaces or underground operation. The results obtained from field measurement campaign carried out at the dam overlooking the village of Saint-Saturnin-les-Apt (South-East of France) are presented. The influences of (i) the host rock body of the barrage and dam’s structure, (ii) the temporal water level variations of the reservoir and (iii) the effect of the temperature on the muons flux measurements are discussed The main challenge that faces the project is that the muon trajectory reconstruction algorithm cannot infer the arrival angles for a non-negligible number of detected events, with the subsequent loss of information. The data collected during the campaign of measurements, should help improving the algorithm’s robustness and reconstruction efficiency. Field transportability and the capability to perform long-term out-of-lab measurements have been demonstrated. The successful proof-of-concept trial makes the MUST2 camera a valuable candidate for transmission muography purposes, particularly in challenging available volume scenarios. The next phase of the T2DM2 project aims at imaging and monitoring the hydrodynamics across the unsaturated zone of the Fontaine-de Vaucluse aquifer. To do so, a network of 20 autonomous detectors will be constructed and deployed within the facilities of the Low Background Noise Laboratory of Rustrel (LSBB), France. The privileged emplacement of the LSBB allows the access to both the surface and to a network of 4 km of underground galleries with depths ranging from 0 to 518 m.